Ceiling support for a medico-technical radiation source

ABSTRACT

The invention relates to a ceiling support for a medico-technical radiation source. The inventive support comprises a telescopic element ( 2 ) consisting of several tubes ( 3 ) which fit in each other and are connected to a compensation weight device of the radiation source connected to the free end (E) of said telescopic element ( 2 ) with the aid of a first cable ( 12 ). The inventive weight compensation device comprises a cable drum ( 11 ) for winding and unwinding said first cable ( 12 ), a helical winch ( 15 ) associated thereto and connected to a sliding element ( 8 ) by means a second cable, said sliding element being displaceable against a pressure spring ( 6 ). The radius of said helical winch ( 15 ) gradually reduces according to the increasing force of the pressure spring ( 6 ) in such a way that the compensation couple of the weight remains identical aside from the respective length of the telescopic element ( 2 ).

RELATED APPLICATIONS

The present application is based on International Application No. PCT/EP2003/012667, filed Nov. 13, 2003, and claims priority from, GermanApplication No. 102 52 931.0,filed Nov. 14, 2002, the disclosure ofwhich is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The invention relates to a ceiling support for holding a technicalmedical radiation source.

BACKGROUND OF THE INVENTION

Such a ceiling support is known for example from U.S. Pat. No.3,175,085.

To compensate the weight of a radiation source installed on the free endof the telescope or telescope arm, a cable is usually led through thetelescope arm which is connected with a device for the compensation ofthe weight. Such a unit can for example include a cable winch driven byan electro motor. With this, however, the radiation source cannot bemoved with the dynamics of a manually adjustable ceiling support.

Furthermore, to compensate the weight, devices are known which include agas pressure or torsion spring. Such units have the disadvantage thatthe weight compensation is not constant over the total extension lengthof the telescope arm. Torsion springs have the further significantdisadvantage of a relatively short lifespan.

In addition, it is known that a helical tension spring is used for theweight compensation and the cable is led over the spiral winch. Althoughthis can be used to achieve an almost constant compensation of theweight over a wide section of the extension length of the telescope arm,a ceiling support using helical tension springs cannot be designedcompactly. Moreover additional technical safety devices must be providedin case the helical tension springs break.

SUMMARY OF THE INVENTION

Object of the invention is to specify a ceiling support to hold atechnical medical radiation source which is designed as simply aspossible, has a long lifespan and can be adjusted over a wide range tothe particular weight of the radiation source.

This object is solved by the features of claim 1. Useful embodimentsresult from the features of claims 2 to 14.

According to the invention, a ceiling support is provided to hold atechnical medical radiation source with a telescope made of severaltelescopable tubes, which telescope is connected via a first cable witha device for the compensation of the weight of a radiation source to beinstalled on the free end of the telescope, wherein the compensationdevice is comprised of:

-   -   a cable drum for winding and unwinding the first cable,

a spiral winch which is permanently connected with the cable drum,

-   -   wherein the spiral winch is connected via a second cable with a        sliding element which can be shifted against the force of a        pressure spring, and    -   wherein a radius of the spiral winch decreases with increasing        pressure of the pressure spring so that a torque compensating        the weight remains essentially the same regardless of the        particular length of the telescope.

The term “cable” is used in connection with this invention generally inthe sense of a means of connection which can be wound. To this extentthe term “cable” also means the means of connection such as for examplea chain, a metal or woven strip, a plastic belt, a plastic cable andsimilar. The exterior circumference of the “cable drum” and the “spiralwinch” is each designed so that the particular “cable” being used can bewound up with this.

The suggested ceiling support is constructed simply. The suggested useof a pressure spring contributes to a significantly improved durabilityand operational safety. Moreover, this permits adjustment of the weightto be compensated within a wide range.

Preferably the spiral winch is installed firmly on the cable drum. Inother words it cannot be turned in relation to the cable drum. In thiscase, the first and the second cable can also be replaced by a singlecable which is connected on the one end with the telescope and on theother end with the movable sliding element. However, in this case, thecable is secured to the end of the cable drum and/or to the end of thespiral winch.

According to an advantageous embodiment, the decrease of the radius isnot linear. It can run similar to a hyperbola. With this, an essentiallyconstant compensation of the weight of the radiation source can beachieved over the entire extension range of the telescope arm. It isuseful that the spiral winch can be designed in the shape of ahyperbolic spiral winch. With a hyperbolic form of the spiral winch, aconstant weight compensation can be achieved in actual practice.

According to a further embodiment, two pressure springs are providedwhich are positioned on guide tubes running parallel to each other. Thesuggested arrangement of the pressure springs on guide tubes contributesto improved break resistance. Even when one of the pressure springsbreaks, the radiation source does not suddenly fall and thus endangerpersons.

It is advantageous that the sliding element is a crosshead which can beshifted on the guide tubes against the force of the pressure springs. Itis useful that the second cable be wound around a roller installed onthe crosshead, mounted with its one end to a frame holding the telescopearm and with its other end to the exterior radius of the spiral winch.The one end of the second cable can also be installed on an outside wallof the telescope arm. The compensation force exerted by the pressuresprings via the crosshead on the spiral winch and thus on the cabledrum, is cut in half by providing the roller as a loose roller based onthe principle of the pulley.

It is furthermore advantageous that the spiral winch be installedbetween the two pressure springs. This can be used to achieve aparticularly compact construction.

To increase operational safety, it is useful to provide two first andtwo second cables. Even when one of the cables breaks, the ceilingsupport remains totally operational. For reasons of technical safety,the spiral winch can in addition be connected with a permanent magnetbrake such that the spiral winch is braked when a power failure occurs.Such a brake is usually only applied when the ceiling support isvertically adjusted. A radiation source held by the ceiling support canthus be additionally secured against an accidentally initiated verticalmovement.

According to a further embodiment, a device is provided to set apre-stress of the pressure spring/s exerted on the sliding element. Thismakes it possible to set a range in which the pressure springs exhibitan almost linear characteristic curve. In addition, a device for thestepless setting of the spring rate can be provided which is usefullyformed as a clamping cuff/s which presses the pressure spring/s againstthe guide tube. This can be used to compensate a further weight area.

According to a particularly preferred embodiment, on an inner sideseveral grooves are provided which axially undercut at least one of thetubes, and guide rails which have an essentially ridge-like form aresecured via a screw connection with groove stones held in the grooves.It is useful to provide three grooves on the inner side of the tubesuniformly over their circumference. The suggested positioning of theguide rails on the inner side of the tubes significantly simplifies themounting of the telescope arm. The guide rails can be shifted radiallyin a certain area while the tubes are being mounted and then be tensedup with the tubes.

BRIEF DRESCRIPTION OF THE DRAWING

An example will now be used to describe the invention in more detailbased on the drawing. The figures are listed below:

FIG. 1 A first view in perspective of the ceiling support,

FIG. 2 A second view in perspective of the ceiling support based on FIG.1,

FIG. 3 A view in perspective of the spiral winch based on FIG. 2,

FIG. 4 A view in perspective of a spiral winch based on FIG. 3 withelectro-motor drive,

FIG. 5 A broken up view in perspective of the ceiling support,

FIG. 5 a A detail view according to section A of FIG. 5 and

FIG. 6 A cross section view through the telescope arm.

DETAILED DESCRIPTON OF THE INVENTION

FIGS. 1 and 2 show a ceiling support in perspective as provided by theinvention. In a rectangular frame 1, a telescope arm 2 approximatelyvertically extended thereto is installed which arm has severaltelescopable tubes 3. The frame 1 is equipped with rollers 4 with whichit can move on rails (not shown here) installed on a ceiling of a room.It is useful that the tubes be made of extruded aluminum profiles. Onthe longitudinal sides of the frame 1 located opposite each other, guidetubes 5 are installed on which at least one—in this example two locatednext to each other—pressure springs 6 are positioned. The one end of thepressure springs 6 is supported against a sleeve 7 installed on each ofthe guide tubes 5, and the other end is supported against a slidablecrosshead 8 installed on the guide tubes 5. A first deflection roller 9which acts like a loose roller is installed in the middle on the side ofthe crosshead 8 which faces the telescope arm 2. The distance of thecrosshead 8 to the axis of the cable drum 11 can be changed with anadjustment screw 9 a. The adjustment screw 9 a can thus be used to setthe tension acting upon the crosshead 8. A support bar element 10 ismounted approximately in the middle of the frame 1 on which element acable drum 11 is installed so that it can be turned. The exteriorcircumference of the cable drum 11 has guiding ridges to hold a firstcable 12. The first cable 12 suggested schematically in FIG. 1 is ledover a second, fixed deflection roller 13 and permanently connected (notshown here) with the tube 3 which forms the free end E of the telescopearm 2. Using a spacer disk 14, a hyperbolic spiral winch 15 is firmlyconnected with the cable drum 11 on the side facing away from thesupport bar element 10. The exterior circumference of the spiral winch15 has guiding ridges for holding a second—in this example two secondcables—cable 16. For the definition of a hyperbolic spiral, reference ismade for example to BRONSTEIN-SEMENDJAJEW, Taschenbuch der Mathematik,18th edition, 1979, page 92.

As can be seen in FIG. 2, the second cables 16 are secured with theirone end in the vicinity of the maximum radius of the spiral winch 15 andwith their other end on the exterior wall of the tube 3 (not shown here)installed on the frame 1. The second cables 16 are also wound around thefirst deflection roller 9.

A permanent magnet brake 17 which is firmly installed with a holder 18on the frame 1 is permanently connected with the spiral winch 15. Anaxis 19 extending from the permanent magnet brake 17 can be optionally(see FIGS. 2 and 4) provided with a pulley 20 which is connected via aV-belt 21 with an electro motor 22 as the drive.

Clamping elements 23 with which the pressure springs 6 can be pressedagainst the guide tubes 5 are provided for setting the spring rate ofthe pressure springs 6. This can be used to steplessly set the length ofthe pressure springs 6 and to select the desired weight range to becompensated.

For the sake of clarity, FIGS. 1 and 2 show the ceiling support withfully extended telescope arm 2 and at the same time with non-compressedpressure springs 6. The functional relationship of the movablecomponents of the ceiling support is not shown there.

The function of the ceiling support is as follows:

A radiation source (not shown here) which is installed on the free end Eexerts a weight on the telescope arm 2. The weight is transmitted viathe first cable 12 and the second deflection roller 13 to the cable drum11. A constant torque corresponding to the weight is exerted on thecable drum 11 and the thereto permanently connected spiral winch 15.This constant torque is compensated by a counter torque exerted on thespiral winch 15. The counter torque is created by the pressure of thepressure springs 6 exerted on the crosshead 8 which is transmitted bythe second cable 16. The pressure which is increasing with increasingcompression of the pressure springs 6 is compensated by a non-linearreduction of the radius of the spiral winch 15 so that the countertorque is constant over the entire extension length of the telescope arm2.

When the telescope arm 2 is completely extended, the pressure springs 6are maximally compressed. The crosshead 8 is shifted by a maximum amountin the direction of the telescope arm 2. In this case, the second cables16 are located on the minimal radius of the spiral winch 15. With upwardmovement of the telescope arm 2, the spiral winch 15 turns so that thesecond cables 16 are wound up by a constantly increasing radius. Thusduring winding up, a continuously larger section of length of the secondcable is wound up per unit of rotation angle of the spiral winch 15.This is accompanied by the simultaneously decreasing pressure of thepressure springs 6 so that the counter torque is held constant.

The permanent magnet brake 17 can be provided optionally to brake ashifting movement of the telescope arm 2. The brake is usefully designedso that the permanent magnet brake 17 brakes the spiral winch 15 whenthe power is interrupted. In case of a power failure, an undesiredshifting movement of the telescope arm 2 cannot occur.

The spiral winch 15 can furthermore be connected via the axis 19 with anelectro motor drive 20, 21, 22. Such an electro motor drive is used tosupport the shifting movement of the telescope arm 2.

The weight to be compensated can be set by adjusting the clamping jaws23 steplessly within a wide range. This makes it possible to change theeffective length of the pressure springs 6.

FIGS. 5, 5 a and 6 show an particularly preferred embodiment of theguidance of the tubes 3. The particularly preferred embodiment of thetubes 3 described below can also be taken by itself for an independentinvention. When the telescope arm 2 is mounted, the problem occurs inactual practice that the guide rails 25 provided on the inner side ofthe tubes must be precisely adjusted to compensate for manufacturingtolerances of the tubes 3. Otherwise, when the telescope arm 2 isextended, the rollers 24 running on the guide rails 25 will lift up. Toensure sufficient pretension of the rollers 24 against the edges of theguide rails 25, the rollers 24 must be secured eccentrically. They canbe pre-tensioned against the guide rails 25 during mounting. Accordingto the preferred example, axially undercutting grooves 26 are providedin the tubes 3. In the essentially triangular profile of the tubes 3shown here, the grooves 26 run along the interior side of the tubes 3approximately in the middle and are staggered by 120°. Groove stones(not shown here) provided with a threading to secure the guide rails 25are threaded into the grooves 26. The guide rails 25 are then connectedwith the groove stones with a screw. For mounting, two tubes 3 are thentelescoped, wherein the guide rails 25 which can still be shifted aresecured on the interior side of the exterior tube 3. The rollers 24 areplaced against the guide rails 25 in the system. Then the interior tube3 is pushed into the exterior tube. Because of this, the guide rails 25adjust themselves automatically. They then only need to be tightened.

REFERENCE DESIGNATION LIST

-   1 Frame-   2 Telescope arm-   3 Tube-   4 Roller-   5 Guide tube-   6 Pressure spring-   7 Sleeve-   8 Crosshead-   9 First deflection roller-   10 Support bar element-   11 Cable drum-   12 First cable-   13 Second deflection roller-   14 Spacer disk-   15 Spiral winch-   16 Second cable-   17 Permanent magnet brake-   18 Holder element-   19 Axis-   20 Pulley-   21 V-belt-   22 Electro motor-   23 Clamping jaws-   24 Roller-   25 Guide rail-   26 Groove-   E Free end

1. A ceiling support for holding a technical medical radia-tion source,with a telescope (2) made of several telescopic tubes (3), which isconnected via a first cable (12) with a device for compensation of theweight of the radiation source to be in-stalled on the free end of thetelescope (2), wherein the device for compensation is comprised of: acable drum (11) for winding and unwinding the first cable (12), a spiralwinch (15) which is connected with the cable drum (11), wherein thespiral winch (15) is connected via a second cable (16) with a slidingelement (8) which can be shifted against the force of a pressure spring(6), and wherein a radius of the spiral winch (15) decreases within-creasing pressure of the pressure spring (6) so that a torquecompensating the weight remains essentially constant regard-less of theparticular length of the telescope (2).
 2. The ceiling support asdefined in claim 1, wherein the spiral winch (15) is installed firmly onthe cable drum (11).
 3. The ceiling support as defined in claim 1,wherein the decrease in the radius is not linear.
 4. The ceiling supportas defined in claim 1, wherein the spiral winch (15) is a hyperbolicspiral winch.
 5. The ceiling support as defined in claim 1, wherein twopressure springs (6) are provided which are positioned on guide tubes(5) running parallel to each other.
 6. The ceiling support as defined inclaim 1, wherein the sliding element is a crosshead (8) which can beslid on the guide tubes (5) against the force of the pressure springs(6).
 7. The ceiling support as defined in claim 1, wherein the secondcable (16) is wound around a roller (9) installed on the crosshead (8),and is secured on its one end to a frame (1) holding the telescope (2)and with its other end at the maximum radius of the spiral winch (15).8. The ceiling support as defined in claim 1, wherein the spiral winch(15) is installed between the two pressure springs.(6).
 9. The ceilingsupport as defined in claim 1, wherein two first (12) and two secondcables (16) are provided.
 10. The ceiling support as defined in claim 1,wherein the spiral winch (15) is connected with a permanent magnet brake(17) such that the spiral winch (15) will be braked when there is apower failure.
 11. The ceiling support as defined in claim 1, whereinthe spiral winch (15) is connected with an electro motor drive (20, 21,22).
 12. The ceiling support as defined in claim 1, wherein a device(23) is provided for the setting of a pre-tension of the pressurespring/s (6) to be exerted on the sliding element (8).
 13. The ceilingsupport as defined in claim 1, wherein a device for the stepless settingof the spring rate is provided which preferably is a clamping cuff (23)which presses the pressure spring (6) against the guide tube (5). 14.The ceiling support as defined in claim 1, wherein several axialundercut grooves (26) are pro-vided on one interior side of at least oneof the tubes (3) so that essentially ridge-shaped guide rails (25) aremounted via a screw connection with the groove stones in the grooves(26).